Recent data continue to indicate that use of the insecticide DDT may have adverse effects on human health, but essentially no findings on this topic have been replicated, so the question is still open. Whether DDT has adverse effects is important because DDT is still used for malaria control in about 12 countries, and current recommendations by the World Health Organization that support DDT use are based on the assumption that it has basically no adverse health consequences for humans. DDE is the major degradation product and metabolite of DDT. Mexico used the insecticide DDT for malaria control until 1999; many people there in tropical areas have elevated blood levels of the DDT metabolite, DDE. My project in Mexico had two phases of field work; both were based on the same group of subjects. I conducted phase 1 of this study to examine the relation between maternal serum levels of DDE in relation to evidence of decreased androgen action in 781 newborn males in Tapachula, Mexico. All phase 1 subjects were enrolled in 2002-2003; the response rate was 95%. Phase 2 of this study began in FY 2004. This study followed 757 women and children enrolled in Phase 1, to determine if DDT exposure is related to reduced length of lactation among mothers. In addition, the offspring were followed to examine early-life DDT exposure in relation to infection and growth. Follow-up has been completed. All of the main papers planned to report finding from Phase 1 and Phase 2 have been published in previous fiscal years. Last years progress: We published a manuscript on DDT and childhood respiratory infections (unlike previous studies in populations with lower levels of exposure, no associations were found). We plan to prepare a similar manuscript on gastrointestinal infections in the coming fiscal year.